In a cellular mobile communication system, a handover method and procedure enables a base node (NodeB) and a user equipment to maintain connection using a single serving carrier and to exchange information. The handover method and procedure may be performed by a procedure that is basically based on connection using the single serving carrier.
A source or serving NodeB providing a service to user equipments may determine a handover with respect to a user equipment that is positioned in a handover region or a handover environment, and may determine a target NodeB based on a measurement result reported by the user equipment, and request the target NodeB for the handover.
A handover request message may include connection information, for example, a Radio Access Bearer (RAB) context that is established with the user equipment.
The target NodeB may review whether it is possible to receive the corresponding user equipment according to a handover request from the source NodeB. When it is possible to receive the corresponding user equipment, the target NodeB may transmit a response message with respect to the handover request.
A handover response message may include a scheduling identifier, that is, a Cell-Radio Network Temporary Identifier (C-RNTI) of the target NodeB for the user equipment to be handed over, radio resource information for a random access, and the like.
The user equipment may receive information associated with the target NodeB together with a handover execution command via the source NodeB. The user equipment having received the information may access the target NodeB. When the connection with the target NodeB succeeds, the user equipment may transmit a handover complete message.
The aforementioned handover method may be suitable for a system that may provide a service using a single serving carrier between the NodeB and the user equipment.
For a NodeB and a user equipment that supports a carrier aggregation using a plurality of carriers, there is a need to introduce an additional operation and control procedure with respect to a source NodeB, a target NodeB, and a user equipment.